Objective To investigate the feasibility of human amniotic mesenchymal stem cells (hAMSCs) transplantation to improve the survival of ischemic ultra-long random skin flap vascularization,so as to promote the survival of skin flap.Methods The hAMSCs were isolated from human amnion,cultured in vitro,and identified by immunocytochemistry.The phenotype of hAMSCs was analyzed by flow cytometry.CellTrackerTM-CM-Dil was used to label before hAMSCs transplantation into skin flap.Twenty SD adult rats were selected and the 2 cm × 8 cm ischemic ultra-long random skin flap models were constructed in the left and right sides of the rat back.The pedicles of flaps were on the lliac crest level.The flaps were divided into left group (injection with 0.5 ml LG-DMEM) and right group (0.5 ml 1 × 106/ml hAMSCs) after the flap was lifted.The survival rate of flap was observed 7 d after surgery.The blood perfusion values,namely blood perfusion unit at pedicle and in the middle,were monitored by laser Doppler flow monitor at the immediate time,24 h,48 h,4 d and 7 d of the skin flap after surgery.The capillary density of the skin flap was observed through histological observation of the tissue (0.5 cm from adult and necrotic junction).The distribution and survival rate of CM-Dil labeled hAMSCs were observed by fluorescent microscope.Results In term of survival rate of the flap,left group was (50.6 ± 2.2) ％,and right group was (70.9 ± 2.1) ％.The survival rate of the flap in right group was greater than that of left group (P ＜ 0.05).Blood perfusion unit detected in the pedicle of left group at days 4 and 7 after surgery was higher than that of the right group (P ＜ 0.05).Blood perfusion unit in middle of flap of left group at 24 h,48 h,4 d and 7 d were lower than that of right group (P ＜ 0.05).The flap capillary density at 7 d after surgery were (8.8 ± 1.2)/mm2 in left group and (23.5 ± 1.6)/mm2 in right group (P ＜ 0.05).The tissue of flap was made frozen section,and the fluorescence microscope showed there were CM-Dil labeled hAMSCs in skip flap in right group,which could manifest the survival and distribution of hAMSCs in skip flap.Conclusion The application of hAMSCs in the middle and distal parts of ultralong random skin flap can significantly improve the survival rate of skin flap,and increase the density of microvascular reconstruction in the flap.